"In order to deliver the broadcast guide service, Rovi has relied on over-the-air traditional broadcast data service providers," wrote spokeswoman Linda Quach in an e-mail explaining that the Santa Clara, Calif., firm's deals with CBS and a PBS subsidiary had expired. "We no longer have agreements in place with these broadcast data service providers."

The shutdown concluded across the United States by the end of April. Many owners of TVGOS hardware probably never noticed, since they use cable or satellite services that feature their own program guides. But a few now have unusable hardware: Some older video recorders used the TVGOS signal to set their clocks but don't allow any manual input of the date and time.

Some still have TVGOS, courtesy of it continuing to be available over the Internet. I'm one of those lucky purchasers, owing solely to the fact that our Sony TV came with that option when we bought it in 2009; a year earlier, and we'd be out of luck too.

If your TV has lost your onscreen guide, you will probably have better luck clicking around its onscreen settings with your remote in search of an Internet-download option than going to its vendor's site for help. My checks at a few either revealed bland confirmations of the TVGOS shutdown or no information at all.

This is a lost opportunity for the industry. Done right, Rovi's system could have made a lot of TV devices smarter, but many manufacturers ignored it entirely. For example, the failure of most DVD recorders to support TVGOS — instead consigning their owners to programming recordings VCR-style by punching in dates and times — helped doom that category of hardware.

It also points to a larger issue for the consumer-electronics industry. Now that so many of our gadgets rely on networked services for core functions, the worry that these services might stop one day can become its own sort of existential electronic dread.

Tip: "MHL" is yet another TV abbreviation you (may) need to remember

Your options for connecting other video devices to a TV have coalesced in recent years to just two: HDMI, an all-digital connection that transfers both audio and video, and component, a trio of analog video cables that must be coupled with some kind of audio connector. And the latter rarely comes into play anymore unless you're dealing with old or malfunctioning hardware.

But a couple of years ago, support for a different kind of connection called MHL, short for "Mobile High-Definition Link," started appearing on the HDMI ports of some new sets--and on the micro-USB ports on certain non-Apple smartphones.